1. Field of the Invention
The present invention relates to methods of producing honeycomb structures and honeycomb structures.
2. Discussion of the Background
Conventionally, various exhaust gas treating apparatuses have been proposed and reduced to practice for internal combustion engines of vehicles, construction equipment and the like. The general exhaust gas treating apparatus is provided with a casing made of a metal or the like, for example, at an intermediate part of an exhaust pipe that is connected to an exhaust gas manifold of the engine, and the honeycomb structure is arranged inside this casing. The honeycomb structure captures particulates included within the exhaust gas, and functions as a filter (DPF: Diesel Particulate Filter) that filters the exhaust gas or, as a catalyst carrier that converts a toxic gas component or the like within the exhaust gas by the catalytic reaction.
For example, in the case where the honeycomb structure is used as the DPF, the honeycomb structure is formed by a plurality of pillar cells that extend in a longitudinal direction of the honeycomb structure, with porous cell walls partitioning the individual cells. Because one end of each of the cells is sealed by a sealant, the exhaust gas that is introduced into the honeycomb structure inevitably passes through the cell wall and is led outside the honeycomb structure. Accordingly, it is possible to capture the particulates or the like within the exhaust gas when the exhaust gas passes through the cell wall. Further, in the case where the honeycomb structure is used as the catalyst carrier, a catalyst carrier layer and the catalyst are provided on the surface of the cell wall in the longitudinal direction of the honeycomb structure. Hence, the toxic gas, such as Co, HC and NOx, included within the exhaust gas can be converted by the catalyst.
For example, the honeycomb structure described above is formed by bonding a plurality of pillar honeycomb units by interposing a bonding layer. This bonding layer greatly affects the characteristics of the completed honeycomb structure, such as the pressure intensity and the adhesion intensity. For this reason, various techniques have been proposed to provide honeycomb structures having desired, satisfactory characteristics, by controlling various characteristics of the bonding layer, such as the porosity and the composition of the bonding layer. For example, such techniques have been proposed in a Japanese Laid-Open Patent Application No. 2006-326831 and Published International Application WO03/067041, the contents of which are incorporated herein by reference in their entirety.